In the LED industry, the manufacturing process of LED chips and the packaging process of LED are independent processes. The LED lighting unit still needs to be cut and tested to form a final chip product no matter what substrate is used in LED epitaxial process. The form of LED chip is usually designed as a rectangular figure due to the consideration of operability in the cutting process despite the LED chip is vertical structure or lateral structure, wire bonding process or flip-chip process. Then, the rectangular LED chip is mounted on a submount by die bonding and welded onto a PCB by method of SMT to form an LED package unit. The LED package unit can also be formed by mounting the chip on a PCB directly (COB method). The package PCB then needs to be mounted and contacted with a heat conductive or a dissipation device to solve the heat dissipation problem, and the heat due to electrical current in the epitaxial structures needs to be dissipated by heat conduction from the substrates to the heat dissipation devices. However, if the electric power or power density is too high, the heat resistance can make the temperature of the LED too high which lowers the life time and optical properties of the LED.
Please refer to FIG. 1, FIG. 1A and FIG. 1B are schematic diagrams illustrating LED chips, LED package and heat dissipation in the prior art. An LED chip 1 is composed of an epitaxial structure 10 and a carrier substrate 11. The LED chip 1 is tested, cut from a wafer, and then packaged to form an LED unit. As shown in FIG. 1A, an LED package unit is formed by mounting the LED chip 1 on a submount 12 with die bonding, wire bonding and phosphor coating processes. In actual application, the LED unit with the submount 12 still needs to be mounted onto a heat conductive PCB, the PCB 13 then is mounted and contacted with a heat dissipation device 14. Another application requirement for high power illumination, as shown in FIG. 1B, an LED package unit is formed by mounting the LED chip 1 on a heat conductive PCB directly (COB, Chip-on-Board). The COB unit is mounted and contacted with a heat dissipation device 14. However, in the prior art of FIG. 1A or FIG. 1B, the manufacturing process for the LED chip 1 and the packaging process of LED are independent processes.
Generally speaking, there are two types of the structures for LED chips, lateral types and vertical types. The lateral type is forming LED epitaxial structures and electrodes on an epitaxial wafer, where the epitaxial wafer needs to go through a thinning process to become a carrier substrate for epitaxial structures and then be cut into LED chips. The vertical type is transferring LED epitaxial structures from an epitaxial wafer to a carrier wafer, where the carrier wafer still needs to go through a thinning process and form electrodes, and then be cut into LED chips. It does not matter whether the LED chip is a lateral type or a vertical type, the LED chips still need an added package substrate to that goes through die bonding, wire bonding and phosphor coating processes to connect an external power and a heat dissipation device. For the demand of high power density, high luminous flux, high working life and low cost, the prior art of FIG. 1A and FIG. 1B still have some limits.